The voice was harder than I had known, and not only in stony reaction to long floods of wholly just selfpity, also roughened with gin and smoke, perhaps also assimilated to New York induration, the hardness of culture as well as of pain.

"At a given degree of induration, massive rocks of sandstone, siltstone, and limestone are the strongest, while shaly rocks with more or less parallel, closely spaced separation surfaces created during sedimentation in thin layers are the weakest." Committee on Underground Coal Mine Safety (1982) Toward Safer Underground Coal Mines Washington, D.C. : National Academy Press, page 32, isbn 978-0-309-03298-8.